The present invention relates to electric motors with electronic commutation and is concerned more particularly with the structure of the latter.
As is known, motors with electronic commutation are composed, inter alia, of a casing which contains a wound armature and a shaft coming out from it. The commutation means of this armature, instead of being constituted by an electromagnetic device made from a commutator and brushes, are in this case an electronic device with a control module.
This type of motor usually poses a difficult problem in manufacturing, in the construction and in the assembly. In fact it is necessary to carry out the construction of the windings which must be housed in slots in the armature, then it is necessary to join the ends of the wires of the windings of this armature with the electronic circuit of the control module and, finally, it is necessary to be able to dissipate the heat from the power components of the electronic circuit of the control module.
In order to join the ends of the wires of the windings with the electronic circuit of the control module, soldering of the wire ends to terminals which are associated with the electronic circuit is usually carried out. Most of the time, taking into account the configuration of the structure of the motor, such soldering can only be done manually. In relatively conventional star connection motors, it is necessary to carry out numerous soldered joints since the armature has multiple windings and each winding requires two soldered joints. Such an operation, which is more particularly difficult to automate, is usually only done manually; it requires therefore a very high degree of skill and is time consuming. In addition, whatever may be the skill of the operator, the soldered joints are subject to contact defects. For example, these soldered joints may be so-called "dry joints", that is the flux additive of the solder flux in fact insulates the wire from the terminal instead of ensuring electrical continuity.
In order to solve another aspect of the problem, there is often used for the electronic device an insulating substrate which carries a conducting printed circuit on which the components of the electronic circuit of the control module are positioned, fixed and connected. Such a substrate, after having been equipped, is usually placed close to one of the end-flanges of the casing of the motor and, preferably, in the vicinity of its internal face. However, as this circuit comprises power components which it is necessary to cool in order to prevent their overheating, which would be destructive, it is seen to it that the insulating substrate is transpierced with apertures and that the power components are fixed directly onto the flange of the motor through these apertures; in this way this flange, by its mass and by its metallic nature, serves as a radiator in order to remove the heat produced in the power components during operation. The fact of having to split up the electronic circuit, in such a manner that several of these components are no longer on the substrate itself but mounted directly on a flange, imposes additional operations in installing, in fixing and subsequently in electrically connecting by soldering these components to the printed circuit of the substrate. It may easily be imagined that this also complicates the operations of mounting and assembly and also is a source of faults.
Another aspect of the difficulties is linked to the construction of the windings of the armature, when it is desirable to carry this out automatically and when the recesses of the armature do not permit prefabrication of these windings in order that they have only to be deposited therein. In such a case, in particular if it is wished to be able to carry this out mechanically or automatically, it is necessary to make use of a winder supplied with an articulated arm rotating about a spindle which is fed with wire by a pay-out which takes it from a reserve. This arm describes a relatively complex trajectory in order, gradually with the unwinding of the wire, to shape it into loops which are successively deposited into the recesses. In order to be able to operate in this way, it is therefore necessary that the armature is relatively uncluttered and easy to access, so as not to obstruct the travel of the rotating hinged arm, in particular by the presence of contactors which receive the ends of the wires of each winding.
One technique which makes it possible to solve some of the difficulties enumerated hereinabove is, for example, explained in the French application No. 8,911,771 filed on Sep. 8, 1989 in the name of the Applicant and published on May 15, 1991, under No. 2,651,933. However, the technique explained therein does not make it possible to carry out, automatically, winding, connecting and then assembly.